Hold-down composition for machining articles

ABSTRACT

A composition for adhering a workpiece to a workholder while a machining operation is performed is disclosed. The composition comprises 10-25 percent by weight of activated charcoal, 1-10 percent by weight of a plasticizer and the balance of a hold-down type wax such as o-terphenyl or paraffin. A method of mixing the ingredients of the composition, applying the mixture to the workpiece and removing same when the work function is completed is also disclosed.

United States Patent 1 1 Shepard 1 Oct. 23, 1973 1 HOLD-DOWN COMPOSITIONFOR 2,462,018 2/1949 Wood ..106/272 MACHINING ARTICLES OTHERPUBLICATIONS [75] Inventor: 2 Shepard San Dlego Kirk- Othmer,Encyclopedia of Chemical Technology," 2nd Edition, Volume 1, page 165,1964. Assigneei hl Industries, Inc., C ula Vista, Bennett, CommercialWaxes, Second Edition, 1956, Calif- Chemical Publishing Co., lnc.,N.Y.C., pages 483, 22 Filed: Jan. 25, 1971 Skeist, Handbook ofAdhesives, Van Nostrand [21] Appl. No.: 109,694

Related US. Application Data [52] 11.8. C1 106/272, 106/287 R, 156/155,156/320 [51] Int. Cl. C08h 9/06, C08h 17/24 [58] Field 01 Search106/272, 271, 287 R, 106/307; 156/155, 320; 161/234, 235; 264/275;208/21 [56] References Cited UNlTED STATES PATENTS 141,829 5/1873 Strong106/272 160,741 l/l875 Alvord 106/272 50,000 9/1865 Havard 106/272Reinhold Company, N.Y.C., 1962, pages 448 and 449.

Primary ExaminerAllan Lieberman Attorney-George E. Pearson [5 7]ABSTRACT A composition for adhering a workpiece to a workholder while amachining operation is performed is disclosed. The composition comprises1025 percent by weight of activated charcoal, l-l0 percent by weight ofa plasticizer and the balance of a hold-down type wax such aso-terphenylor paraffin. A method of mixing the ingredients of the composition,applying the mixture to the workpiece'and removing same when the workfunction is completed is also disclosed.

2 Claims, N0 Drawings 1 HOLD-DOWN COMPOSITION FOR MACHINING I ARTICLES 1CROSS-REFERENCE This application is a division of my copendingapplication for Hold-Down Composition for Machining Aritcles, Ser. No.741,287, filed July 1, 1968, now u.s. Pat. No. 3,586,559.

BACKGROUND OF THE INVE TION This invention relates generally to adhesivehold down compositions for adhering a workpiece to a workholder and moreparticularly to a composition of matter for holding metal honeycomb to'a workpiece 'holder in a secure yet readily removable manner while somework-function is applied to it.

In the manufacture of parts from metal honeycomb blocks, the workpiecemust be temporarily but securily bonded to. a workpiece holder whilesome work function such as cutting, shaping, 'etc., is applied to it..Byits nature, honeycomb cannot readily be clamped, gripped or secured inany of the conventional manners to the holder. The problem of bondingthe honeycomb to the .workholder in a temporary manner has bothered theindustry for a number of years with numerous techniques having beensuggested and utilized for the noted function. In general, some form ofan adhesive has been relied on in the past to perform the hold-downfunction. Various materials suchas wax, soap, ice, a type of sugarcandy, waterglass and many others have been suggested and used. All ofthese materials are similar in that they respond to a rise intemperature to free the workpiece after the work function has beenperformed or the application of water to the bonding material breaks thebond thereby freeing the workpiece. All of the suggested known materialsexhibit numerous disadvantages such as poor adhesion, low adhesivestrength, difficult handling characteristics, inability to be applied tonon-horizontal surfaces, difficulty of removal, etc

It is therefore desired to remedy the disadvantages of the prior artmaterials while retaining all of their known desirable characteristics.In particular it'is desired to Obtain a method and apparatus forfastening a honeycomb workpiece or other structure "to a workholder in asimple yet effective'manner with a minimum of difficulty and withoutcausing any deleterious effects to the materials used. I

SUMMARY OF THE INVENTION An object of this invention therefore is toprovide an adhesive for temporarily bonding a workpiece to a workholderwhile a machining operation is performed thereon.

Another object of this invention is to provide a holddown compositionand method for holding a honeycomb workpiece to a workholder.

Yet another object of this invention is to provide an improved.hold-down composition which is readily removable when so desired.

A more particular object of this invention is to provide a compositionand a method for adhering a section of honeycomb foil to a workholderina removable manner while the foil is machined.

A still more particular object of this invention is to provide acomposition and method for adhering contoured honeycomb foil sections toa workholder.

The instant invention achieves the above noted objects by adding to awax-type hold-down composition a quantity of finely divided activatedcharcoal in a proportion within the range of 10 25 percent by weight. Asuitable long chain plasticizer can also be added to improve the workingcharacteristics of the new composition. The composition of thisinvention is applied in a method comprising heating the composition toabove its melting point, applying it to a workholder, bringing theworkpiece in contact with the workholder, and cooling the composition tobelow its melting point causing it to assume its solid form and adherethe workpiece to the workholder. The workpiece may then be later removedby reheating the composition to above its melting point. Any residualcomposition remaining on the workpiece or workholder can be readilyremoved by vapor degreasing and hot alkaline cleaning.

The above noted objects and features of this invention will be betterunderstood from the following detailed description and appended claims.

DETAILED DESCRIPTION As indicated, the purpose of the presentinvention-is to thicken a hold-down type wax without lessening any ofits ability to provide adequate adhesion or tensile strength to adhere aworkpiece to a holder and, further,

- to avoid any change in the material which might make it difficult toremove after an adequate bond was effected by it. Furthermore theadditive material must not be of a nature'whereby the material of theworkpiece may be damaged by corrosion or other deleterious reactions.The desired effect and result is accomplished by adding finely dividedactivated charcoal to a hold-down type wax. A plasticizer may also beadded to provide a wetting agent function, aid in the mixing of thecharcoal with the wax, and lower the solidification temperature toprovide a longer application, or working, time. The addition of theplasticizer also re sults in a final composition having a finer and morehomogenous texture.

In searching for an adhesive which would meet the exacting requirementsof this method, a number of compounds were tested. A wide range of waterinsoluble waxlike materials, long chain plasticizers and powders havebeen found which are suitable, however, the preferred composition is awater insoluble waxlike material such as o-terphenyl or paraffin,strengthened by the addition of a powder such as finely dividedactivated charcoal, and, in the case of o-terphenyl, plasticized with along chain material such as paraffins or ethylene oxide condensates ofphenols. The charcoal powder serves the additional function ofthickening the wax material to simplify application to a non-horizontalsurface. Itis advisable to vary the proportion of plasticizer to suitthe conditions such as the adhesive 1 strength needed or the amount ofworking time rebelow 10 percent by weight the desired thickening isinsufficient and handling characteristics are therefor undesirable.

Considering the plasticizer, it was determined that a range of from 1 10percent by weight produced the best results. The addition of plasticizerin amounts less than 1 percent fails to achieve the desired benefits forwhich the addition of the plasticizer is intended. Furthermore, theaddition of plasticizer in amounts greater than 10 percent by weightresults in the creation of a composition which tends to be too plasticand never hardens sufficiently to achieve the desired adhesive effect.In view of the limited solubility of the plasticizer in the solid wax,the addition of too much of same results in the excess being driven outof solution to the interface between the adhesive composition and theadjacent workpiece or workholder. The effect of the latter is to preventa secure surface bond between the noted parts.

It the hold-down wax used is paraffin, it has been found that theplasticizer is not necessary and consequently may be omitted from thecomposition.

The following examples illustrate three embodiments of a hold-downcomposition made in accordance with this invention. The percentagesgiven represent percent by weight in the total composition.

EXAMPLE 1 Activated Charcoal powder l-25% Plasticizer l-l0% O-terphenylwax Balance EXAMPLE 2 Activated Charcoal powder l0-25% O-terphenyl waxBalance EXAMPLE 3 Activated Charcoal powder -25% Paraffin wax Balance lnthe composition of Examples 1 and 2 the oterphenyl used was that soldunder the tradename of Santo Wax-O and manufactured by the MonsantoCompany. The plasticizer of Example 1 was that sold under the tradenameTriton X-lOO by Rohm and Haas. Nuchar C-l 90N activated charcoal powderas supplied by the Matheson Chemical Company, Inc. was used in eachexample. i

The composition of Example 1 is prepared by the method which follows.The o-terphenyl is first heated and raised to above its meltingtemperature, preferably to a temperature within the range of 200 240F.The plasticizer is then mixed in with the o-terphenyl. Activatedcharcoal powder is then added with vigorous mixing until the desiredconsistency is reached. The charcoal should be added in a manner tominimize dust blowing yet assure complete mixing. It may be observedthat lumps sometimes form during the mixing process, however these arereadily broken up. Mixing should continue until all of the charcoalpowder is evenly dispersed throughout the mixture. The composition soprepared may be used immediately or poured into a mold to be cooled andstored as a cake and reserved for later use. It is only necessary tore-heat and stir the already prepared but cooled composition when it isto be applied.

The composition of Example 2 and 3 is prepared in essentially the samemanner as that of Example 1 with the elimination of the step requiringthe addition of the plasticizer. In other words, the o-terphenyl orparaffin is heated to approximately 200 240F and the charcoal powder inthe desired proportion is thoroughly mixed therewith.

Each of the exemplary compositions is intended for a specific use.Example 1 is preferred for general usage with contouredworkpieces/workholders. It is essentially a compromise between ultimatestrength and workability. The plasticizer tends to decrease the ultimatestrength while increasing the workability by lowering the hardeningtemperature and hence lengthening the hardening time.

The Example 2 composition is best suited for those applications wherethe highest adhesive strength is desired and workability is of no greatconsequence. Typically, it has its greatest utility in the bonding offlat surfaces where the composition can be quickly applied.

Example 3 has the least strength of the group but tends to be moreflexible, or plastic, even when hardened. This latter characteristicmakes it desirable where the workpiece must yield somewhat during amachining process.

All of the embodiments of the instant invention are used in a'manner ormethod to be described. After choosing a composition with the properproportions to suit the character of the workpiece and workholder, thechosen composition is prepared for use by heating to a temperaturewithin the range of 200 240F and stirring thoroughly. It is then appliedto the workholder by some suitable means. The exact means of applicationmay be varied to suit the particular situation. It has been noted thatthe adhesive composition of this invention may be spread with a trowelor allowed to flow down an inclined tool face for example. In the lastmethod the adhesive composition forms a stable uniform coating with athickness depending upon the viscosity of the particular composition.

Better adhesion can be obtained, and application simplified, if theworkholder is warmed to F before the composition is applied. Throughcontrol of tool and adhesive temperatures, considerable application timecan be arranged. Long application times may be desired, as previouslynoted, to facilitate application of the composition to contouredsurfaces or the like.

After the adhesive composition has been applied to the surface of theworkholder, the workpiece is positioned over the workholder and force isapplied to conform the workpiece to the workholder. After such a step,the edges of the workpiece that are adjacent to the workholder will besubmerged in the adhesive composition. When the temperature of all theparts and the composition is then allowed to lower to a point belowwhich the composition resumes its solid state, the workpiece will berigidly attached to the workholder. The desired machining operations canthen be performed.

When it is desired to remove the workpiece, it is merely necessary toelevate the temperature of the composition to above its melting point.It has been found that for this purpose an array of heat producingelectrical lamps provides sufficient melting. The workpiece can then bereadily removed. A residual quantity of the composition may remain onthe workpiece after it is removed from the workholder, however, same mayreadily be removed by vapor degreasing and/or hot alkaline cleaningtechniques. Any residue on the workholder of course can be removed inthe same manner.

It may be further noted that as in any other adhesive process, both theworkpiece and the workholder should be cleaned to remove any possiblecontaminants before the composition is applied. In the case of metalhoneycomb foil, for example, cleaning in a trichloroethylene degreaserfollowed by complete drying adequately prepares the structure for thebonding.

In accordance with this invention then, it should be apparent that asimple but yet effective composition, a method of making same, and amethod for adhering a workpiece to a workholder have been disclosed.Although the invention has been described with respect to threeparticular embodiments thereof, it should not be limited thereto forvarious changes and modifications could be made by one having ordinaryskill in the oxide condensates of phenols.

2. The composition of claim 1 further including 1-10 percent by weightof a long chain plasticizer selected from the group consisting ofparaffin and ethylene oxide condensates of phenols.